A flash memory capable of retaining memories even when a power supply is turned off is used in a mobile device such as a cellular phone, and is now widely used.
A memory cell of the flash memory is constructed by forming, on a semiconductor substrate, a tunnel insulating film, a floating gate, an intermediate insulating film, and a control gate in this order. Such memory cells are integrally formed on the semiconductor substrate along with a peripheral circuit to construct a flash memory.
Such a flash memory is disclosed, for example, in Japanese Patent Application Publication Nos. 2005-129760, 2005-142362, and 2005-244086.
Various patterning processes are performed in a flash memory manufacturing process. For example, a conductive film is patterned into the control gate. If an excessive film is left after patterning has been performed, the film is peeled off, and reattached to other area. Consequently, patterning defect occurs in that area, resulting in reduction in the production yield of the semiconductor device.
In a process of manufacturing not only a flash memory but also a common semiconductor device, the deformation of a device pattern of a floating gate and the like becomes notable due to an optical proximity effect in an exposing process as the pattern is increasingly miniaturized. In order to prevent such a pattern deformation, shape correction referred to as OPC (Optical Proximity Correction) is usually performed on the light-shielding pattern of a reticle (exposure mask), so that the projected image of the light-shielding pattern becomes a designed shape of the device pattern.
For example, repeated patterns of stripe patterns are subjected to the OPC in Japanese Patent Application Publication No. Hei 1-188857, where the corner of each pattern is obliquely cut off by the OPC.